JPH02252968A - Idling revolution speed controller for two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To secure the stable idling operation without installing a special device by controlling the valve opening time of an air blast valve which jets out fuel and compressed air into a combustion chamber so that the engine revolution speed becomes equal to an aimed revolution speed, in the engine idling operation. CONSTITUTION:An engine is equipped with an air blast valve 9 which jets out fuel, together with compressed air, into a combustion chamber 4. The air blast valve 9 is drive-controlled through a driving circuit 59 by the control signal outputted from an electronic control unit 50 into which a variety of detecting signals supplied from an engine revolution speed sensor 26, etc., are inputted. In this case, in the idling operation of the engine, the valve opening time of the air blast valve 9 is controlled so that the engine revolution speed becomes equal to an aimed revolution speed. In other words, in the idling operation of the engine, the operation of a mechanical supercharger 12 is suspended, and combustion is carried out only by the compressed air jetted from the air blast valve 9, and the jetted-out compressed air is controlled properly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an idling speed control device for a two-stroke internal combustion engine.

[Conventional technology]

A two-stroke internal combustion engine is known in which fresh air is supplied into a fuel chamber by a mechanical supercharger, and fuel is injected into the fuel chamber together with compressed air from an air blast valve (Japanese Patent Laid-Open No. 6
3-246411).

In this two-stroke internal combustion engine, the intake valve is kept closed during idling, and combustion is performed only with fuel and compressed air supplied from the air blast valve.

[Problem to be solved by the invention]

However, when fuel and air are simply injected from the air blast valve during idling, there is a problem in that the idling speed fluctuates.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, in a two-stroke internal combustion engine equipped with an air blast valve that injects fuel into a combustion chamber together with compressed air, a rotation speed sensor that detects the engine speed is provided, and the engine is idle. The opening time of the air blast valve is controlled so that the engine speed reaches the target speed during operation.

[For production]

The engine speed is maintained at the target speed by controlling the opening time of the air blast valve.

〔Example〕

FIG. 1 shows an overall diagram of a two-stroke internal combustion engine.

Referring to FIG. 1, ■ is a cylinder block, 2 is a piston that reciprocates within the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is a cylinder formed between the piston 2 and the cylinder head 3. combustion chamber,
Reference numeral 5 indicates an intake valve, 6 indicates an intake port, 7 indicates an exhaust valve, 8 indicates an exhaust port, and 9 indicates an air blast valve that injects fuel together with compressed air into the combustion chamber 4. Although not shown in the drawings, an ignition plug is arranged at the center of the inner wall surface of the cylinder head 3. The air supply port 6 is connected to a surge tank 11 via an air supply branch pipe 10, and the surge tank II is connected to an air cleaner 15 via an engine-driven mechanical supercharger 12, an air supply duct 13, and an air flow meter 14. be done. A throttle valve 16 is arranged within the air supply duct 13.

FIG. 2 shows an enlarged sectional view of the air blast valve 9.

Referring to FIG. 2, the housing 30 of the air blast valve 9
A compressed air passage 31 extending straight is formed inside.
At the tip of this compressed air passage 31 is a combustion chamber 4 (see Fig. 1).
A nozzle opening 32 located inside is formed. An on-off valve 33 is disposed within the compressed air passage 31, and a valve body 34 for controlling opening and closing of the nozzle port 32 is integrally formed at the outer end of the on-off valve 33. A movable core 36 that is disposed coaxially with the on-off valve 33 and urged toward the on-off valve 33 by a compression spring 35, and a solenoid 37 for attracting the movable core 36 are arranged within the housing 30.

The inner end of the on-off valve 33 is connected to the movable core 3 by a compression spring 38.
Since the spring force of the compression spring 38 is stronger than the spring force of the compression spring 35, the nozzle port 32 is normally closed by the valve body 34 of the on-off valve 33.

When the solenoid 37 is energized, the movable core 36 closes the on-off valve 3.
As a result, the valve body 34 of the on-off valve 33 opens the nozzle port 32. On the other hand, from the compressed air passage 31, a compressed air passage 3 extending diagonally from the compressed air passage 31 is provided.
9 is branched, and this compressed air passage 39 is connected to a compressed air supply port 40. A fuel injection valve 41 is provided in the housing 30.
is attached, and fuel is injected into the compressed air passage 39 from the nozzle hole 42 of this fuel injection valve 41.

As shown in FIG. 1, an air blasting air passage 17 is branched from the air supply duct 13 between the air flow meter 14 and the throttle valve 16.
7 is an engine-driven vane pump 18 and a compressed air passage 1
It is connected via 9 to a compressed air distribution chamber 20 . This compressed air distribution chamber 20 is connected to a compressed air supply port 40 of an air blast valve 9 provided for each cylinder. A pressure regulating valve 21 is disposed in the compressed air passage 19 to maintain the compressed air pressure in the compressed air distribution chamber 20 at a predetermined constant pressure, and excess compressed air is returned to the supply air via the compressed air return passage 22. It is returned into the duct 13. The compressed air passages 31, 39 of the air blast valve 9 are therefore filled with compressed air at a constant pressure.

FIG. 3 shows the opening period of the intake valve 5 and the exhaust valve 7, the period of fuel injection from the fuel injection valve 41, and the valve body 34 of the on-off valve 33.
, that is, the opening period (■) of the air blast valve 9. As shown in FIG. 3, in the embodiment shown in FIG. 1, the exhaust valve 7 opens before the intake valve 5 and closes before the intake valve 5. Furthermore, as shown in FIG. 3, before the valve body 34 of the on-off valve 33 opens, that is, before the air blast valve 9 opens, the compressed air in the compressed air passage 39 is injected from the fuel injection valve 41. Fuel is injected towards the target. Next, when the air blast valve 9 opens, the injected fuel flows from the nozzle port 32 into the combustion chamber 4 together with the compressed air.
Injected inside. On the other hand, as shown in FIG. 1, a mask wall 23 is formed on the inner wall surface of the cylinder head 3 to cover the opening of the intake valve 5 on the exhaust valve 7 side over the entire valve period of the intake valve 5.

Therefore, when the intake valve 5 opens, fresh air is supplied from the intake boat 6 into the combustion chamber 4 through the opening of the intake valve 5 on the opposite side to the exhaust valve 7. As a result, the fresh air flows along the peripheral wall surface of the fuel chamber 4 as shown by arrow S, thus achieving good loop scavenging.

As shown in FIG. 1, the air blast valve 9 is controlled based on an output signal from an electronic control unit 50. This electronic control unit 50 has a ROM (IJ-only memory) 52 and a RAM connected to each other by a bidirectional bus 51.
(random access memory) 53, a CPU (microprocessor) 54, an input port 55, and an output port 56. The air flow meter 14 generates an output voltage proportional to the amount of intake air, and this output voltage is input to the input port 55 via the AD converter 57.

Further, a water temperature sensor 24 that generates an output voltage proportional to the engine cooling water temperature is attached to the cylinder block l, and the output voltage of the water temperature sensor 24 is inputted to an input port 55 via an AD converter 58. Further, a throttle switch 25 is attached to the throttle valve 16 to detect that the throttle valve 16 is at an idling opening, and an output signal of the throttle switch 25 is inputted to an input port 55 .

Furthermore, an output signal from the rotation speed sensor 26 representing the engine rotation speed is inputted to the input port 55 . On the other hand, the output boat 56 is connected to the air blast valve 9 via a corresponding drive circuit 59,60.
The solenoid 37 and fuel injection valve 41 are connected to the solenoid 37 and the fuel injection valve 41.

Further, the mechanical supercharger 12 is connected to the engine crankshaft via an electromagnetic clutch 27 and a belt 28. Therefore, when the electromagnetic clutch 27 is turned on and brought into the engaged state, the mechanical supercharger 12 is driven by the engine, and when the electromagnetic clutch 27 is turned off and brought into the disengaged state, the mechanical supercharger 12 is stopped. The electromagnetic clutch 27 is connected to the output boat 56 via the drive circuit 61, and therefore the electromagnetic clutch 27 is controlled by the output signal of the electronic control unit 50.

During engine operation, fresh air is forced into the combustion chamber 4 from the air supply boat 6 by the mechanical supercharger 12, and fuel and compressed air are injected into this fresh air from the air blast valve 9. However, when the required amount of fresh air is small, such as when the engine is idling, the compressed air jetted from the air blast valve 9 can cover the required amount of fresh air. Therefore, in the embodiment according to the present invention, the mechanical supercharger 12 is stopped when the engine is idling, and combustion is performed only with the compressed air jetted from the air blast valve 9. By stopping the mechanical supercharger 12 during engine idling in this manner, drive loss of the mechanical supercharger 12 is eliminated, and thus the fuel consumption rate can be improved.

Furthermore, especially in a two-stroke internal combustion engine, the engine speed during idle-link operation tends to become unstable. Therefore, in the embodiment according to the present invention, the amount of compressed air injected from the air blast valve 9 is controlled so that the idling rotation speed becomes the target rotation speed. In this case, as described above, the compressed air pressure in the compressed air passages 31 and 39 in the air blast valve 9 is maintained constant, and therefore the amount of compressed air injected from the air blast valve 9 is controlled by the opening of the air blast valve 9. It will be proportional to the valve time. By the way, in the embodiment shown in FIG. 1, the closing timing IC (FIG. 3) of the air blast valve 9 is fixed, so by changing the opening timing 10 (FIG. 3) of the air blast valve 9, the air The opening time of the blast valve 9 is controlled.

Next, control of the electromagnetic clutch 27 and the air blast valve 9 will be explained with reference to FIGS. 4 to 7.

FIG. 4 shows a control routine for the electromagnetic clutch 27, and this routine is executed by interruption at regular intervals.

Referring to FIG. 4, first, in step 70, the output signal of the throttle valve 16 is determined from the output signal of the throttle switch 25.
It is determined whether or not the opening degree is the idling opening degree. If the throttle valve 16 is at the idling opening, step 7
1, and the engine rotation speed N is determined from the output signal of the rotation speed sensor 26 to a predetermined setting value NO1, for example, 1000r,
It is determined whether or not p and m are lower. When N<No, the process advances to step 72 and the electromagnetic clutch 27 is turned off.

That is, the throttle valve 16 is at the idling opening, and the N
<If No, it is determined that the engine is idling, and the electromagnetic clutch 27 is turned off, and as a result, the mechanical supercharger 12 is stopped. Then, in step 73, the clutch flag is reset.

On the other hand, whether the throttle valve 16 is open or N≧
If No, the process proceeds to step 74, where the electromagnetic clutch 27 is turned on, and therefore, the mechanical supercharger 12 is activated at this time. Next, in step 75, a clarification flag is set.

FIG. 5 shows the air blast valve 90 control routine. This routine is executed at a predetermined crank angle after top dead center.

Referring to FIG. 5, first, in step 80, the fuel injection time TA of the fuel injection valve 41 is determined from the output signal of the air flow meter 14 representing the intake air amount and the engine rotation speed N.
U is calculated. Next, in step 81, it is determined whether the clutch flag is set. When the clutch flag is set, that is, when the mechanical supercharger 12 is activated, the routine proceeds to step 82, where the control flag is reset. Next, in step 83, the opening time IT of the air blast valve 9 is set to a predetermined constant value ITO. Next, in step 84, the opening period I (FIG. 3) of the air blast valve 9 expressed in crank angle is calculated by multiplying the opening period IT of the air blast valve 9 by the engine speed N and a constant K. Next, in step 85, the opening start timing IO of the air blast valve 9 is calculated by subtracting the opening period I from the closing timing IC of the air blast valve 9. As shown in FIG. 3, before the bottom dead center, fuel is injected from the fuel injection valve 41 for a fuel injection time TAU, and when the crank angle reaches the opening start timing 10 of the air blast valve 9, the air blast valve 9 opens. Fuel is injected together with compressed air through the valve.

On the other hand, when the mechanical supercharger 12 is stopped during the period of idling operation and the clutch flag is reset, the process proceeds from step 81 to step 86, where it is determined whether or not the control flag is set. At this time, since the control flag has been reset, the process advances to step 87 and the control flag is set. Next, in step 88, the initial value of the opening time IT of the air blast valve 9 is calculated from the relationship shown in FIG. 7 based on the output signal of the water temperature sensor 24 representing the engine cooling water temperature T. Next, in steps 84 and 85, the opening timing IO of the air blast valve 9 is calculated, and the air blast valve 9 is opened for the opening time IT.

In the next processing cycle, the process proceeds from step 86 to step 89, where the target rotational speed NO is calculated from the relationship shown in FIG. 6 based on the output signal of the water temperature sensor 24 representing the engine cooling water temperature T. As shown in FIG. 6, when the engine cooling water temperature T is higher than a predetermined set temperature, for example 80°C, the target rotation speed No. is set to 600r, for example.11. m,
When the engine cooling water temperature T is lower than 80° C., the target rotation speed NO increases as the engine cooling water temperature T decreases. Next, in step 90, the engine rotation speed N becomes the target rotation speed NO+Δ
It is determined whether or not it is higher than N (ΔN is a small constant value).

If N>No+ΔN, the process proceeds to step 91, where a constant value α is subtracted from the opening time IT of the air blast valve 9. As a result, the amount of fuel and compressed air injected from the air blast valve 9 is reduced, and the engine speed N is reduced. On the other hand, N4N.

When it is ten α, the process proceeds to step 92, where it is determined whether N<No−ΔN. When N<NO-ΔN, the process proceeds to step 93, where a constant value α is added to the opening time IT of the air blast valve 9. As a result, the amount of fuel and compressed air injected from the air blast valve 9 is increased, so that the engine speed N increases. In this way, the engine rotation speed N is maintained near the target rotation speed No.

Note that the initial value of the opening time IT of the air blast valve 9 shown in FIG. 7 is approximately equal to the target rotation speed NO.
Therefore, the initial value of the valve opening time IT becomes a curve similar to the target rotation speed NO. The relationships shown in FIGS. 6 and 7 are stored in the ROM 52 in advance.

〔Effect of the invention〕

Since the idling rotation speed can be maintained at the target rotation speed, stable idling operation can be ensured. Further, by using the air blast valve for idling speed control, there is an advantage that there is no need to separately provide a special idling speed control device.

[Brief explanation of drawings]

Fig. 1 is an overall view of a two-stroke internal combustion engine, Fig. 2 is an enlarged side sectional view of the air blast valve, Fig. 3 is a line diagram showing the opening periods of the supply and exhaust valves, the opening periods of the air blast valve, etc. Figure 4 is a flowchart for controlling the electromagnetic clutch, Figure 5 is a flowchart for controlling the air blast valve, Figure 6 is a diagram showing the target rotation speed, and Figure 7 is the opening time of the air blast valve. FIG. 3 is a diagram showing initial values of . 5...Air supply valve, 7...Exhaust valve, 9...
・Air blast valve, 12... Mechanical supercharger, 27.
...Electromagnetic clutch. Diagram

Claims (1)

[Claims] A two-stroke internal combustion engine equipped with an air blast valve that injects fuel into the combustion chamber together with compressed air is equipped with a rotation speed sensor that detects the engine rotation speed so that the engine rotation speed reaches the target rotation speed when the engine is idling. An idling speed control device for a two-stroke internal combustion engine that controls the opening time of an air blast valve.